We've studied life on Earth extensively, but we still have no idea where it came from. Some scientists think it may have spontaneously arisen on Earth by some unknown process. Others think the ingredients for life were delivered here by comets crashing into Earth in the early days of the solar system.
The latter theory just got a huge boost, thanks to new research published April 8 in the journal Science.
The key result: Scientists simulated the vacuum of space and created a key ingredient in RNA — an essential molecule for all the forms of life that we know about.
Demonstrating that the precursors for RNA could form in space is huge, because many scientists think the first life forms on Earth were RNA-based.
For the experiment, Meinert and the team essentially built a fake comet by recreating the ice that the European Space Agency's Philae lander found on Comet 67P back in 2014.
The team chilled ammonia, methanol and water inside a vacuum to recreate the comet ice. Next, they dowsed the ice with UV light to simulate the radiation that a comet would encounter in space.
The experiment produced 55 organic molecules. The most important one was ribose — a key sugar that makes up RNA.
"There is evidence for an 'RNA world' — an episode of life on Earth during which RNA was the only genetic material," Cornelia Meinert, one of the researchers who worked on the new study, told Space.com. "At a certain point in prebiotic evolution, the availability of ribose would have been, therefore, necessary for life to have started."
The results of the experiment fit in with real-world observations of comet 67P: Scientists have already found organic material on it.
So it's looking more possible that we owe our existence to comets that crashed into Earth when the solar system was first forming, delivering the necessary ingredients to kickstart life.